FDA scrutinizes infection risk with Amgen drug

WASHINGTON 
Federal health officials are questioning increased infection rates and tumors seen with an osteoporosis drug from Amgen that analysts say is key to the company's growth.

The Food and Drug Administration said Tuesday that patients taking Amgen Inc.'s denosumab were more likely to develop infections of the skin, ear and urinary tract than patients taking placebo.

Biotech drugmaker Amgen wants the FDA to approve denosumab as a treatment for postmenopausal osteoporosis and for the prevention of bone loss in patients being treated for breast and prostate cancer. About 10 million Americans have osteoporosis, which causes bones to thin and fracture, and nearly 45 million are at increased risk due to low bone density.

The drug is a genetically engineered version of a protein that helps block the breakdown of bone cells. But the FDA is concerned the drug, which also affects the immune system, can leave patients more vulnerable to infection.

On Thursday, the FDA will ask a panel of experts whether additional safety restrictions or studies are needed to make sure denosumab can be used safely. The agency is not required to follow the experts' advice, though it usually does. The FDA is scheduled to make a decision on denosumab by October.

With millions of U.S. seniors at risk for bone fractures, denosumab represents a significant market opportunity for Amgen, with analysts predicting sales between $1 billion and $2 billion. Wall Street has pegged the company's future growth to denosumab, as sales of its anemia drugs continue to slide on safety labeling restrictions.

Lazard Capital Markets analyst Joel Sendek said Amgen should be able to address the FDA's safety questions later this week.

"Based on the briefing documents, which did not reveal any new safety or efficacy concerns, we anticipate that the advisory panel will likely vote for denosumab approval," Sendek wrote in a note to investors.

Shares of Amgen rose $1.25, or 2 percent, to $62.49 in afternoon trading.

"There is an increased risk of serious skin infections with denosumab that is important to the overall benefit risk assessment," the FDA said in its review.

Amgen has proposed labeling to warn patients "to seek prompt medical attention if they develop signs or symptoms of cellulitis," a serious type of skin infection.

Regulators also have concerns about higher rates of malignant tumors seen with denosumab. In data pulled from six studies of the drug conducted by Amgen, women taking denosumab were more likely to develop tumors of the breast, intestine and reproductive system.

Regulators have become increasingly concerned that some biotech drugs can hasten tumors, after recent studies of Amgen's anemia treatments showed faster tumor growth in cancer patients.

If approved, denosumab would enter a $4.9 billion U.S. market for osteoporosis treatments and bone density drugs, which includes GlaxoSmithKline PLC's Boniva and Merck & Co. Inc.'s Fosamax, according to data from IMS Health.

While there are no head-to-head studies comparing bone fractures with denosumab versus those drugs, medical experts say Amgen's treatment could be easier for patients to use than older drugs. Whereas tablet drugs must be taken on a daily or weekly basis, denosumab is injected twice a year, reducing the chance that patients will stop taking their medication.

With eight other pills and injectable medicines on the market, including low-cost generic versions of Fosamax, denosumab's success likely will hinge on its price. Amgen has not yet discussed pricing for denosumab, which would be marketed as Prolia, but its closest potential competitor, Novartis' injectable drug Zometa, sells for about $1,300 per year.

A spokeswoman for Thousand Oaks, Calif.-based Amgen said the company will try to keep the drug affordable but declined to be more specific.

Denosumab also is under review in the European Union, Australia and Switzerland, where it would be marketed by British drugmaker GlaxoSmithKline.